HeatPumpDo You Need New Radiators for a Heat Pump?
One of the most common concerns about heat pumps: "Will I need to rip out all my radiators?" The honest answer is: probably not all of them, and maybe none at all. Here's how to work out what your home actually needs.
Why Flow Temperature Matters
A gas boiler pushes water through your radiators at 55–75°C. A heat pump works most efficiently at 35–45°C. That's a significant difference, and it's the reason radiators come into the conversation.
Lower water temperature means each radiator emits less heat per hour. If a radiator was sized to keep a room warm with 70°C water, it might struggle at 40°C. The solution is straightforward: use a bigger radiator that emits the same heat at the lower temperature.
When You Don't Need New Radiators
Many UK homes — especially older properties — have radiators that were oversized when originally installed. This is actually good news. If your radiators are bigger than your rooms need, they'll work fine at lower flow temperatures.
Signs your existing radiators may be fine:
- Your current boiler's thermostat is set below 60°C and rooms heat up comfortably
- Rooms reach temperature quickly and the boiler cycles off frequently
- Radiators feel warm (not hot) to the touch when the heating is on
- You've improved your insulation since the radiators were installed (reducing the heat demand of each room)
When You Do Need to Upgrade
Radiator upgrades are likely needed when:
- Radiators are small, old-style single-panel designs
- Your home is poorly insulated with high heat loss
- Rooms currently struggle to reach temperature even with the gas boiler
- The heat loss calculation shows the existing radiator output is insufficient at 45°C flow
The general rule: radiators for a heat pump need to be 1.5 to 2 times larger than those needed for a gas boiler. This doesn't always mean replacing them — sometimes adding an extra radiator to a room, or swapping a single-panel for a double-panel convector, is enough.
Radiator Upgrade Costs
| Item | Cost (supply + fit) |
|---|---|
| Single radiator upgrade | £200–£400 |
| 3-bed house (4–6 radiators) | £800–£2,400 |
| 4-bed house (6–8 radiators) | £1,200–£3,200 |
| Fan convector radiator (premium) | £400–£800 each |
Not every radiator needs replacing. A good installer will do a room-by-room heat loss calculation and identify exactly which radiators need upsizing. You might only need to change 2–3 radiators in a 3-bed house.
Types of Heat-Pump-Friendly Radiators
Double-panel convectors (Type 22): The most common upgrade. Two panels with convector fins deliver roughly 1.5–2x the heat output of a single panel at the same wall space. Cost-effective and widely available.
Triple-panel convectors (Type 33): Maximum output for the wall space. Slightly deeper (around 10cm) but ideal for rooms with limited wall space.
Fan convectors: A premium option with a built-in fan that actively blows warm air through the radiator. They deliver high output at very low flow temperatures (even 35°C) and heat rooms quickly. More expensive (£400–£800 each) but excellent for problem rooms.
The Smart Approach: Insulate First
Before spending money on new radiators, improve your insulation. Better insulation reduces the heat your rooms lose, which means your existing radiators may actually be adequate at heat pump flow temperatures without any upgrades.
Cavity wall insulation (£1,000–£1,500), loft insulation (£300–£600), and draught-proofing (£200–£400) together can reduce your home's heat demand by 30–50%. That's often enough to avoid radiator replacements entirely.
Mixing Radiators with Underfloor Heating
A popular retrofit approach is to install underfloor heating in key living areas (living room, kitchen, bathroom) and keep radiators in bedrooms and hallways. Both systems run at the same low flow temperature, and the heat pump handles them through a single system. Underfloor heating is the ideal emitter for a heat pump, while radiators are quicker and cheaper to install in rooms where floor work isn't practical.
What Your Installer Should Do
A competent MCS-certified installer will perform a room-by-room heat loss calculation as part of the system design. This determines exactly how much heat each room needs and whether the existing radiators can deliver it at the planned flow temperature. If any installer tells you "all radiators need replacing" without doing this calculation, get another quote. See our guide to choosing an installer.
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Frequently Asked Questions
Do heat pumps work with normal radiators?
Yes, heat pumps work with standard radiators. However, because heat pumps run at lower flow temperatures (35–45°C vs 55–75°C for gas boilers), your radiators may need to be larger to deliver the same heat output. If your existing radiators are already oversized for their rooms — which is common in older houses — they may work perfectly as they are.
How much does it cost to upgrade radiators for a heat pump?
Budget £200–£400 per radiator including supply and installation. A typical 3-bed house needing 4–6 new radiators would cost £800–£2,400. Not all radiators need replacing — a heat loss survey will identify which rooms need upgrades.
What flow temperature does a heat pump use?
Air source heat pumps typically run at 35–45°C flow temperature for maximum efficiency. This is lower than a gas boiler (55–75°C), which is why radiators may need to be larger to compensate.
Can I mix radiators and underfloor heating with a heat pump?
Yes, and this is actually a popular approach. Underfloor heating in living areas and kitchens (where it works best) combined with upsized radiators in bedrooms. The heat pump can supply both at the same low flow temperature.